THE INVENTION relates to a dosing means for facilitating the drawing of a predetermined volume of a liquid, to be injected, into a hypodermic syringe having an axially displaceable plunger, the dosing means including a positioning element providing a formation to receive and locate the syringe body and means capable of limiting withdrawal of the syringe plunger to a first axial position with respect to said positioning element.
Such dosing means, known through U.S. Pat. No. 4,248,225, for instance, are of great help to diabetics who have poor eyesight, enabling them to measure the correct dose of insulin themselves.
However, very many diabetics nowadays require two different types of insulin, a quick-acting and a slow-acting insulin. This necessitates either two injections, which is undersirable in view of the difficulty and unpleasantness caused to the patient or, which is preferable, the incorporation of the desired doses of the two types of insulin into a single charge in a hypodermic syringe for administration to the patient in a single injection.
Conventional dosing means of the character referred to above are unsuitable for this purpose, i.e. for accurate measurement of respective doses of two liquids for injection drawn into a hypodermic syringe to form a single charge, since two different dosing means with different markings must be used, a first dosing means being used for the first dose and a new dosing means replacing the first dosing means after the first measured dose has been drawn into the hypodermic syringe, in order to assist in measurement of the second dose to be drawn up.
If the dosing means according to U.S. Pat. No. 4,248,255 is used, for instance, a first dosing means, marked for the first dose, must be applied on the finger grip of the hypodermic syringe, the needle of the syringe inserted in first ampoule, and the plunger drawn out until it comes into contact with a stop on the first dosing means, after which the first dosing means and ampoule are removed and a second dosing means, marked for the second dose, applied on the finger grip. An ampoule with a second injection composition is then applied over the tip of the hypodermic syringe after which the plunger is drawn out until it comes into contact with the stop of the second dosing means. It will be readily understood that besides the difficulty in dealing with two different dosing means, it is troublesome for a patient with poor eyesight and perhaps impaired coordination to carry out these different procedures correctly. There is also a considerable risk of the patient unintentionally moving the plunger during the exchanging procedure, so that some of the first injection liquid is lost and either the patient obtains an incorrectly proportioned dose or the entire procedure must be repeated.